Left side chest pain from 4 months.

I am getting left side chest pain which is like crushing pinching and like shock sometimes.i don't get usually during playing and walking but during the starting I get.i got echo Threadmill and ECG where it was normal , also got endoscopy got which was normal also taking daily 2 times pan 40 from 3 months , even chest X ray was normal but this pain is continues during resting and more I'm the left side of the chest it usually comes in upper part then middle and down and most times on the left side of the chest..it usually comes like a shock and some times on the middle some unusual beats are twitches type sensation comes , I rarely smoke one per day and a social drinker..but I am not a regular one..but this pain comes daily and when I take tablets like ultracet it temporary relieves but not permanent